Mobile and wireless technology is growing at a rapid rate. These advances have resulted in breakthroughs that have made feasible new applications of data communication. For example, in areas in which there is little or no communication infrastructure, or the existing infrastructure is expensive or inconvenient to use, wireless mobile users may still be able to communicate through the formation of an ad hoc network.
In an ad hoc network, each mobile node operates not only as a host but also as a router, forwarding packets for other mobile nodes in the network that may not be within direct wireless transmission range of each other. Each node participates in an ad hoc routing protocol that allows it to discover “multi-hop” paths through the network to any other node.
Since ad hoc networks lack an infrastructure, ad hoc networks allow for unrestricted mobility and new communication uses. For example, a collaborative office or training environment may be readily created with laptop computers and computer peripherals capable of wireless communication with one another. As another example, a battlefield command and control system may allow the sharing of sensor and command information between wireless nodes carried on military vehicles and by soldiers. As yet another example, emergency personnel may coordinate logistics and relief actions in an austere environment such as the site of an earthquake or other natural disaster. As yet a further example, intelligent wireless sensor networks may be mounted on mobile platforms.
Merely being able to communicate by wireless transmission is not enough for a reliable network since networks in general have a number of security requirements. Information should be transmitted and stored by the network in a confidential manner so that only authorized parties may read it. Information should be transmitted so that integrity is maintained, preventing unauthorized parties from altering the information (e.g., writing, deleting, changing status, creating, or replaying). Information should be subject to access control by or for the target (receiving) node. In addition, the assets of the network should be available to authorized parties, and thus not be unduly susceptible to denial of use attacks.
Wireless transmissions are generally more prone to attacks that impact these security requirements. For instance, the wireless transmission may be susceptible to the attacks of eavesdropping, replay, and spoofing. These security requirements are complicated by the nature of ad hoc networks. Mobile nodes tend to have power constraints, either due to the use of portable power supplies or due to physical and regulatory constraints on the radiated power of the wireless transmission. Often mobile nodes are constrained in the processing speed and memory storage to reduce the amount of heat generated, power consumption, size, and cost. In addition, wireless communications is more easily intercepted and disrupted than hard-wired communication media.
Authentication of mobile nodes and the source of communication from mobile nodes is a crucial guarantee for many of these security concerns. Unauthenticated messages may be discounted, reducing the potential harm that may result from relying upon an untrustworthy communication. In conventional wireless networks, base stations are fixed and share secret keys with mobile nodes. The base station acts as a certification authority (CA) for authenticating mobile nodes that are in its purview. The CA needs to be a completely trusted entity that issues a digital certificate to any mobile node that needs to be authenticated. A sending node uses the digital certificate, or digital signature, by sending it along with a message encrypted with a private key. Upon receipt, the receiving node decrypts the message with a public key.
Strong authentication in conventional wireless networks thus requires base stations, significant processing overhead by mobile nodes to use a public-private key encryption for each message, and thus significant power consumption. These constraints are undesirable or unavailable in ad hoc networks.
Consequently, a significant need exists for a method for authenticating mobile nodes and communication within an wireless network, especially an ad hoc network.